Automobiles primarily employ monocoque bodies instead of frame bodies, because they are lightweight and excellent in productivity. A monocoque body is a structure that obviates a separate frame, and a powertrain, which is constituted by coupling an engine and a transmission to each other, is directly mounted to a vehicle body.
Therefore, in a vehicle manufactured of a monocoque body, suspension and chassis parts are mounted to a vehicle body because the vehicle body itself functions as a frame. However, in order to prevent vibrations of a powertrain from being directly transferred to the vehicle body and to disperse shocks in an event of a vehicle collision, a subframe and mounting members are mounted to the bottom of the vehicle.
The subframe is mounted to the bottom of the vehicle body so that a steering device and a suspension device, such as a suspension strut and a knuckle, can be connected thereto. The mounting members include an engine mount, which is installed to a portion of the vehicle body and is secured to an engine, a transmission mount, which is installed to another portion of the vehicle body and is secured to a transmission, and a roll-rod for connecting the engine or the transmission to the subframe.
Accordingly, the transmission mount supports the weight of the powertrain applied to the transmission and also has a vibration isolation function of preventing vibrations from the powertrain from being transferred to the vehicle body.
Referring to FIG. 1, a conventional rubber-type transmission mount 3 is structured such that an insulator 5, which is formed of an elastic material (for example, rubber or synthetic resin), and a metal core 6 are coupled to each other and are inserted together into a housing 4, which is formed in a shape of a container having a predetermined size, and such that one end portion of the metal core 6 protrudes outwards through an opening 4a, which is formed in a portion of the housing 4 that is oriented toward a transmission bracket 2 when mounted to the vehicle body. The end surface of the core 6 has a bolt hole formed therein, and the transmission mount 3 is coupled to the transmission bracket 2, which is mounted to the transmission 1, through the bolt hole by using a bolt. Accordingly, the transmission mount 3 supports the weight of the powertrain applied to the transmission and isolates vibrations of the powertrain owing to elastic deformation of the insulator 5.
Further, the transmission mount 3 additionally includes a stopper 7 in order to prevent the insulator 5 and the housing 4 from being damaged due to a sudden increase in the load that is transferred to the insulator in accordance with the traveling conditions of the vehicle.
The conventional stopper 7 has a shape of a ring that communicates with the opening 4a and is bonded to the periphery of the opening 4a. The stopper 7 has a rib 7a, which protrudes upwards from the lower side thereof in order to prevent the core 6 from moving downwards at a predetermined distance or more, thereby suppressing excessive elastic deformation of the insulator 5.
However, the conventional stopper 7 contributes to the durability in a vertical direction of the insulator since the stopper 7 controls only the downward movement of the core 6, but does not control a load in a width direction of the vehicle (a lateral direction), which is generated due to a gap between the transmission bracket 2 and the housing 4, thereby providing a negative effect on the steering performance of the vehicle.
Further, a separate stopper is bonded to the external portion of the transmission mount 3 in order to control the displacement of the powertrain when the vehicle is steered, thereby improving a sense of unity between the powertrain and the vehicle body and improving steering responsiveness and steering-tracking performance of the vehicle when the vehicle turns sharply. However, the bonding portion (the adhering portion) can be weakened by frequent turning of the vehicle, thus greatly deteriorating the robustness of the bonding.
The insulator 5 of the transmission mount 3 is secured to the bracket, and the bracket is coupled to the vehicle body. At this time, the insulator 5 of the transmission mount 3 connects the mount bracket to the powertrain (PT), and a lower bridge, which is formed integrally with the insulator 5, is formed of rubber and supports the weight of the powertrain and isolates vibrations of the powertrain. The bridge is deformed in accordance with the movement of the powertrain and consequently allows the movement of the powertrain. However, if the movement of the powertrain is excessive, when the vehicle turns sharply, the powertrain moves in the direction opposite the direction in which the vehicle turns according to the principal of action and reaction, and this movement of the powertrain may reduce a sense of unity between the powertrain and the vehicle body and may provide a negative effect on steering-tracking performance of the vehicle.
Therefore, there is a need to develop a stopper structure for the transmission mount, which may suppress movement of the powertrain so as to improve the steering performance, and which may securely fix a noise/shock-preventing bracket so as to prevent separation of the bracket and to reliably prevent the occurrence of noise.